I wrote sampsize mostly because I needed a small utility to easily compute sample size for surveys, particularly surveys of events with low probability of occurrence, and sample or power of comparative studies.
T Test (Student's T-Test): Definition and Examples ...
The t test (also called Student's T Test) compares two averages and tells you if they are different from each other.The t test also tells you how significant the differences are; In other words it lets you know if those differences could have happened by chance.
This is the minimum recommended size of your survey. If you create a sample of this many people and get responses from everyone, you're more likely to get a correct answer than you would from a large sample where only a small percentage of the sample responds to your survey.
6. Power and Sample Size. The power of an experiment is the probability that it can detect a treatment effect, if it is present.. The six factors listed here are intimately linked so that if we know five of them we can estimate the sixth one.
Two Sample t Test: equal variances - Real Statistics
How to use the t test in Excel to determine whether two independent samples have equal means where the variances are unknown but equal. Also describes how to calculate Cohen's effect size and Hedges' unbiased effect size.
Sample Size Calculator for Comparing Two Independent Means
A free on-line program that calculates sample sizes for comparing two independent means, interprets the results and creates visualizations and tables for evaluating the influence of changing input values on sample size estimates.
Sample size procedure to calculate the size of a sample necessary to compare two independent samples, one sample against a fixed value or parameter and sample size calculation for correlated or paired samples.
Effect size calculator - The Hong Kong Polytechnic University
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